1. Field of the Invention
This invention generally relates to methods and apparatus for prosthetic implant devices. More particularly, the present invention relates to prosthetic implants for joints that are conformable, preferably both at the time of implant and over the life of the implant.
2. Background Art
The replacement or augmentation of joints with artificial or prosthetic implants is well known in the field of orthopedics. Total knee arthroplasty (TKA) procedures involving the replacement of the knee joint are a good example. U.S. Publ. Appl. 2003/0028196A1 and the PFC RP Knee Replacement manual provide a good background for the techniques and devices used as part of these arthroplasty procedures.
The prosthetic implant devices for use in arthroplasty procedures are typically metallic devices or devices that have a combination of metallic and plastic components. Because of the high loads and strains that these devices must endure for years, almost invariably the design of these prosthetic implant devices relies on the rigid structure and durability of the metallic components to support the loads and strains. While the rigid structure and durability of metallic implants is beneficial in most regards, these features make the fit or interface between the metallic implant and the resected bone surface critical to the long term viability of an implant.
In total knee replacements, for example, a series of planar and/or curvilinear surfaces, or “resections,” are created to allow for the attachment of prosthetic or other devices to the femur, tibia and/or patella. In the case of the femur, it is common to use the central axis of the femur, the posterior and distal femoral condyles, and/or the anterior distal femoral cortex as guides to determine the location and orientation of distal femoral resections. The location and orientation of these resections are critical in that they dictate the final location and orientation of the distal femoral implant. It is commonly thought that the location and orientation of the distal femoral implant are critical factors in the success or failure of the artificial knee joint. Additionally, with any surgical procedure, time is critical, and methods and apparatus that can save operating room time, are valuable. Past efforts have not been successful in consistently and/or properly locating and orienting distal femoral resections in a quick and efficient manner.
Over the years, alternatives to metallic prosthetic implants have been proposed. U.S. Pat. Nos. 3,906,550 and 4,693,721 describe a porous metallic fabric for use as a medical implant. U.S. Pat. No. 5,986,169 describes a porous nickel-titanium metal alloy for use as a medical implant. European Publ. Appl. 0 761 242 A1 describes a molded polymer orthopedic implant with a bearing surface formed of a porous metal layer. PCT Publ. Appl. WO 02/34310 A2 describes a shape memory polymer material that is used as a connective tissue replacement material for orthopedic applications. These alternatives have met with little success or acceptance in the orthopedic implant field.
It would be desirable to provide for an orthopedic prosthetic implant that could be implanted more consistently and effectively, yet provided or exceeded the ideal long term wear and stability of current rigid metallic implants.